DE0-NANO Board SDC file and PLL

Changing the SDC file will not change the FPGA design or the board or the behaviour of any of the components on the board. There is a fixed 50MHz oscillator on the Nano.

If you want to run everything at 30MHz then you either need to de-solder 50MHz oscillator and replace it with a 30MHz part - don't do this - or, far more practically, use one of the PLLs in your FPGA to generate the 30MHz clock from the 50MHz. Use the IP catalogue in Quartus to locate a PLL and configure it to your needs. Then instantiate it in your design.

The 'derive_pll_clocks' in your SDC file will then deal with everything required to check that the design will run at the revised frequency.

Cheers,

Alex